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%I #12 Jul 23 2017 16:37:25
%S 4,0,0,0,80,40,368,352,5296,3744,48656,40208,523808,415488,5270976,
%T 4333504,54215264,44497728,551297184,458337984,5613555008,4691821600,
%U 56981627840,47988689152,577641089664,489273948160,5845628996352
%N Number of open knight's tour diagrams of a 3 X n chessboard that have "type X": both endpoints occur in the same column.
%D D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010.
%H Seiichi Manyama, <a href="/A169770/b169770.txt">Table of n, a(n) for n = 4..1000</a>
%H George Jelliss, <a href="http://www.mayhematics.com/t/oa.htm">Open knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3a (21 October 2000).
%H George Jelliss, <a href="http://www.mayhematics.com/t/ob.htm">Closed knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3b (21 October 2000).
%H D. E. Knuth <a href="/A169770/a169770.txt">Generating functions for A169770-A169777 and A169696.</a>
%F Asymptotic value 0.000169*n*3.11949^n when n is even, 0.0000526*n*3.11949^n when n is odd.
%Y Cf. A070030, A169696, A169764-A169777.
%K nonn
%O 4,1
%A _N. J. A. Sloane_, May 10 2010, based on a communication from _Don Knuth_, Apr 28 2010
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